Existing rack and shelving units use corner posts to support longitudinal supports across which horizontal or slightly inclined shelves are placed. The longitudinal supports have metal end fittings with numerous prongs extending therefrom or perpendicular thereto and shaped to fit into numerous shaped openings in the corner posts. The fabrication of these connectors is complex and costly. It also takes time to fit the shaped protrusions into the shaped recesses and even more time to undo such connections if the shelving is to be removed or repositioned. There is thus a need for a simpler way to connect shelves to vertical supports such as corner posts.